Wired Intelligent Edge

May someone explain the different please

From the manuals:

• "Uni-directional link detection (UDLD) monitors a link between two switches and blocks the ports on both
  ends of the link if the link fails at any point between the two devices."
• "Device link detection protocol (DLDP) is switch technology that detects any unidirectional link failures that can occur in a network."
• Upon detecting a link failure, the link PHY will be kept UP and will be blocked in the hardware.
• All the upper layer protocols of the switch software (STP, LACP, etc.) will see the interface as DOWN.

To my knowledge, UDLD is a Cisco proprietary protocol. It is described in an informational RFC 5171, contrary of what you might find it is not a standard:

This document describes a Cisco Systems protocol that can be used to detect and disable unidirectional Ethernet fiber or copper links caused, for instance by mis-wiring of fiber strands, interface
   malfunctions, media converters' faults, etc.  It operates at Layer 2
   in conjunction with IEEE 802.3's existing Layer 1 fault detection
   mechanisms.

HPE uses the term DLDP for the exact same functionality as UDLD, I have not tested it but it might be fun to do a packet capture of UDLD and DLDP and see what the difference is.

Both protocols are used to identify unidirectional links but are not interoperable. The devices of each side of the link must be configured to use the same protocol. The below table gives you an overview which switch os will support what protocol. DLPD was originally the Comware OS implementation which was later implemented in AOS-S switches too that those work together.

This document describes a Cisco Systems protocol that can be used to detect and disable unidirectional Ethernet fiber or copper links caused, for instance by mis-wiring of fiber strands, interface   malfunctions, media converters' faults, etc.  It operates at Layer 2   in conjunction with IEEE 802.3's existing Layer 1 fault detection   mechanisms.